Effective discovery and sharing of process models within and/or across enterprises are important in process model management. A semantic annotation approach has been applied for specifying process semantic heterogeneity in the semantic process model discovery in our previous work. In this paper, the approach is further developed into a complete and systematic semantic annotation framework. Four perspectives are tackled in our framework: basic description of process models (profile annotation), process modeling languages (meta-model annotation), process models (model annotation) and the purpose of the process models (goal annotation). Ontologies, including modeling ontology, domain specific ontology and goal ontology, are used for annotation of process models to achieve semantic interoperability. A set of mapping strategies are defined to guide users to annotate process models.